Low Evaporation Rate Storage Vessel for Liquid Helium

Expressions are derived for the heat flux q₀ and temperature gradient dT/dh in a Pyrex cylinder (a) in vacuo and (b) in the atmosphere of cold vapor issuing from a liquid helium container. In the temperature range 20<T<300 we find for case (a) that q₀ α T^1.8 and dT/dh α T^−0.8, while in case (b) q₀ $\mathrm{\alpha ̇}$ T and dT/dh is nearly constant. Design details and operating procedures are given for a 12‐liter liquid helium storage vessel intended to complement our Collins helium liquefier. It can be filled in one day's operation of the liquefier, and ten days later is still half full.